Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University , Wuhan, 430079, P. R. China.
Environ Sci Technol. 2014;48(1):272-8. doi: 10.1021/es403667b. Epub 2013 Dec 16.
Contamination of water and soils with arsenic, especially inorganic arsenic, has been one of the most important topics in the fields of environmental science and technology. The interactions between iron and arsenic play a very significant role in the environmental behavior and effect of arsenic species. However, the mechanism of As(III) oxidation in the presence of iron has remained unclear because of the complicated speciation of iron and arsenic. Photooxidation of As(III) on nascent colloidal ferric hydroxide (CFH) in aqueous solutions at pH 6 was studied to reveal the transformation mechanism of arsenic species. Experiments were done by irradiation using light-emitting diodes with a central wavelength of 394 nm. Results show that photooxidation of As(III) and photoreduction of Fe(III) occurred simultaneously under oxic or anoxic conditions. Photooxidation of As(III) in the presence of nascent CFH occurred through electron transfer from As(III) to Fe(III) induced by absorption of radiation into a ligand-to-metal charge-transfer (LMCT) band. The estimated quantum yield of photooxidation of As(III) at 394 nm was (1.023 ± 0.065) × 10(-2). Sunlight-induced photooxidation of As(III) also occurred, implying that photolysis of the CFH-As(III) surface complex could be an important process in environments wherein nascent CFH exists.
水和土壤中砷的污染，特别是无机砷的污染，一直是环境科学与技术领域的重要课题之一。铁与砷的相互作用在砷物种的环境行为和效应中起着非常重要的作用。然而，由于铁和砷的复杂形态，As(III)在铁存在下的氧化机制仍不清楚。本研究通过使用中心波长为 394nm 的发光二极管辐照，研究了水溶液中 pH 值为 6 时初生胶体氢氧化铁（CFH）上 As(III)的光氧化作用，以揭示砷物种的转化机制。结果表明，在有氧或缺氧条件下，As(III)的光氧化和 Fe(III)的光还原同时发生。在初生 CFH 的存在下，As(III)的光氧化通过辐射吸收到配体-金属电荷转移（LMCT）带中引起的电子从 As(III)转移到 Fe(III)而发生。在 394nm 处，As(III)光氧化的估计量子产率为（1.023±0.065）×10(-2)。太阳光诱导的 As(III)光氧化也发生了，这意味着 CFH-As(III)表面络合物的光解可能是存在初生 CFH 的环境中的一个重要过程。
